The leaders of Japan and the United States have made a historic visit to Pearl Harbour, in a gesture aimed at proving that even the bitterest enemies can become allies.

Prime minister Shinzo Abe did not apologise for the 1941 attack that catapulted America into the Second World War, but conceded Japan "must never repeat the horrors of war again".

Seventy-five years after Japan's surprise attack on the Hawaii navy base, Mr Abe and US president Barack Obama peered down at the rusting wreckage of the USS Arizona, clearly visible in the tranquil, teal water.

More than 1,000 US war dead remain entombed in the submerged ship and in a show of respect, Mr Obama and Mr Abe scattered purple petals on the water and stood in silence.

"As the prime minister of Japan, I offer my sincere and everlasting condolences to the souls of those who lost their lives here, as well as to the spirits of all the brave men and women whose lives were taken by a war that commenced in this very place," Mr Abe said later at nearby Joint Base Pearl Harbour-Hickam.

It was the closest Mr Abe would get to an apology for the attack, but it was enough for Mr Obama, who also declined to apologise seven months ago when he became America's first sitting president to visit Hiroshima, where the US dropped an atomic bomb in a bid to end the war.

It was enough, too, for Alfred Rodrigues, a 96-year-old US Navy veteran who survived the Pearl Harbour attack. He said he had no hard feelings, adding: "War is war."

"They were doing what they were supposed to do, and we were doing what we were supposed to do," he said before the visit.

Mr Abe, who became Japan's first leader to visit Pearl Harbour with a US president, said the visit "brought utter silence to me". His remarks capped a day that was carefully choreographed by the US and Japan to show a strong and growing alliance between former foes.

They started with a formal meeting at another nearby military base, in what the White House said was probably Mr Obama's last meeting with a foreign leader before leaving office in January.

It was a bookend of sorts for the president, who nearly eight years ago invited Mr Abe's predecessor to be the first leader he hosted at the White House.

Mr Obama, speaking after he and Mr Abe laid green-and-peach wreaths at the memorial, called Pearl Harbour a sacred place and said that "even the deepest wounds of war can give way to friendship and lasting peace".

It is a notion Mr Obama tried throughout his presidency to put into practice, as he reached out to former adversaries Iran, Burma and Cuba.

"As we lay a wreath or toss flowers into waters that still weep, we think of the more than 2,400 American patriots, fathers and husbands, wives and daughters, manning heaven's rails for all eternity," he said.

Then the two leaders greeted survivors in the crowd. They shook hands and hugged some of the men who fought in the December 7 1941 battle that President Franklin D Roosevelt called a "date which will live in infamy".

Japanese leaders have visited Pearl Harbour before, but Mr Abe was the first to go to the memorial above the sunken USS Arizona, where a marbled wall lists the names of US troops killed in the Japanese attack.

For Mr Abe, it was an act of symbolic reciprocity, coming seven months after Mr Obama and Mr Abe visited Hiroshima together and renewed their calls for a nuclear-free future. Still, both governments maintain that the visits were separate and not contingent upon one another.

The visit was not without political risk for Mr Abe, given the Japanese people's long, emotional reckoning with their nation's aggression in the war.

Though the history books have largely deemed Pearl Harbour a surprise attack, Japan's government still insists it had intended to give prior notice that it was declaring war and failed only because of "bureaucratic bungling".

"There's this sense of guilt, if you like, among Japanese, this 'Pearl Harbour syndrome', that we did something very unfair," said Tamaki Tsukada, a minister in the Japanese embassy in Washington. He said he believed Mr Abe's visit would "absolve that kind of complex that Japanese people have".

In the years after Pearl Harbour, the US incarcerated about 120,000 Japanese-Americans in internment camps before dropping atomic bombs in 1945 that killed some 140,000 people in Hiroshima and 70,000 in Nagasaki.

Since the war, the US and Japan have built a powerful alliance that both sides say has grown during Mr Obama's tenure, including strengthened military ties.

Yet there are questions about whether the relationship will degenerate under US president-elect Donald Trump, a possibility neither Mr Obama nor Mr Abe addressed.